Synthetic ester lubricants containing trihydrocarbyl tin sulfides and phenothiazines



United States Patent 3,511,782 SYNTHETIC ESTER LUBRICANTS CONTAINING TRIHYDROCARBYL TIN SULFIDES AND PHE- NOTHIAZINES Robert E. Malec, Birmingham, Mich., assignor to Ethyl gtu'poration, New York, N.Y., a corporation of -2 No Drawing. Filed May 29, 1967, Ser. No. 642,205 Int. Cl. Cm 1/54, 1/38 U.S. Cl. 25246.4 11 Claims ABSTRACT OF THE DISCLOSURE Petroleum-derived and synthetic hydrocarbon lubri cants, ester lubricants, polyglycol lubricants, phosphate ester lubricants, silicones, silicate esters, fluoroe'sters, and polyphenyl ethers are stabilized against the effect of oxy''- gen by the synergistic combination of phenothiazine and a trihydrocarbyl tin sulfide. For example, the stabilizing efiect of phenothiazine on di(2-ethylhexyl)sebacate is synergized by tributyl tin sulfide.

BACKGROUND The stabilization of lubricants, especially ester type lubricants, with phenothiazine is known (R. C. Gunderson et al., Synthetic Lubricants, p. 193, Reinhold Publishing Company, New York (1962)). At elevated temperatures the quantity of stabilizer required results in sludging of the lubricant. Hence, a need exists to provide stabilization of lubricants with a reduced amount of phenothiazine that will not result in sludging.

SUMMARY An object of this invention is to provide lubricating oils of enhanced stability. A further object is to provide lubricants that can be used under adverse conditions such as elevated temperatures in the presence of oxygen for extended periods of time. A still further object is to provide an ester type lubricant especially useful in turbine engines.

These and other objects are accomplished by providing a synergistic stabilizer comprising from about 10 to 99 weight percent of a phenothiazine and from 1 to about 90 weight percent of trihydrocarbyl tin sulfide wherein the hydrocarbyl radicals contain from about 1 to carbon atoms.

In a preferred'embodiment the stabilizing composition comprises from about 75 to 99 weight percent of phenothiazine and from 1 to about weight percent of the trihydrocarbyl tin sulfide.

Useful phenothiazines include both substituted phenothiazine and unsubstituted phenothiazine. These can be represented by the following formula:

N R H R wherein each R is selected from the group consisting of hydrogen, alkyl groups containing 1 to 20 carbon atoms, aryl groups containing 6 to 20 carbon atoms, aralkyl radicals containing 7 to 20 carbon atoms, halogen and hydroxyl. Examples of suitable substituted phenothiazines are: 1,9-dimethyl phenothiazine, 1,9-diethyl phenothiazine, 3,7-diphenyl phenothiazine, 1,9-diethyl-3,7-dichloro phenothiazine, 3,7-dihydroxy phenothiazine, 1-methyl-9- benzyl phenothiazine, 3.7-dibromo phenothiazine, 3,7-ditert-butyl phenothiazine, 3,7-dioctyl phenothiazine, 1,3,7,

3,511,782 Patented May 12, 1970' ice wherein each R represents a hydrocarbyl radical containing from 1 to about 20 carbon atoms. Examples of these are trimethyl tin sulfide, triethyl tin sulfide, methyldiethyl tin sulfide, tri(Z-ethylbutyl) tin sulfide, tri-n-dodecyl tin sulfide, trieicosyl tin sulfide, triphenyl tin sulfide, phenyldibutyl tin sulfide, tri (3,5-di-sec-heptylphenyl) tin sulfide, tribenzyl tin sulfide, dibenzyl butyl tin sulfide, u-methylbenzyl dimethyl tin sulfide, and the like. Likewise, mixtures of the trihydro-carbyl tin sulfides can be employed as well as compounds having different hydrocarbyl substituents on the tin atom. The more preferred trihydrocarbyl tin sulfides are trialkyl tin sulfides wherein the alkyl groups are lower alkyl groups containing from 1 to about 12. carbon atoms. The most preferred trihydro carbyl tin sulfide is tributyl tin sulfide. I

The amount of the synergistic combination employed in lubricant compositions depends on the particular lubricant being stabilized, the use conditions, and the degree of stabilization required. All that is necessary is that an amount be employed such that satisfactory stabilization of the lubricant is obtained. In general, good results are obtained when from 0.01 to 5 weight percent phenothiazine and from 0.0005 to 0.5 weight percent trihydrocarbyl tin sul-fiide are present in the lubricant. A more preferred use range is from about 0.1 to 3 weight percent of the phenothiazine and from about 0.001 to 0.3 Weight percent of the trihydrocarbyl tin sulfide. A most preferred cencentration range in the lubricant is from about 0.2 to 1.0 weight percent of the phenothiazine and from about 0.005 to 0.1 weight percent of the trihydrocarbyl tin sulfide.

The synergistic stabilizers can be used in a wide range of base lubricants such as petroleum-derived hydrocarbon lubricants and synthetic hydrocarbon lubricants such as polybutenes, ester lubricants, polyglycols, phosphate esters, silicones, silicate esters, fiuoroesters, polyphenyl ethers, and the like. These base lubricants, their proper ties, and methods of preparation are adequately disclosed by Gunderson et al. in Synthetic Lubricants, Reinhold Publishing Company, New York (1962).

The petroleum-derived hydrocarbon lubricants include those of a wide viscosity range of from about SAE-S to SAE-SO. These lubricants can be prepared using any of the well-known refining methods such as solvent refining and can be of the aromatic, naphthenic or parafiinic type.

Synthetic hydrocarbon oils are those lubricants derived from the polymerization of low molecular Weight olefins such as propylene, butene, isobutene, pentenes, hexenes, octenes, and mixtures of such monomers. The polymerization can be brought about by the use of catalysts such as aluminum chloride. The polymer oils have a wide range of molecular weights and vis cosities.. For example, the polybutene oils have viscosities ranging from 40 to over 3,000 SUS at 210 -F., which corresponds to molecular weights of from 300 to about 1500. The flash point of .these polybutene oils varies from about 200 to 500 F. and their pour points range from about -,65 F. to about 35 F.

The polyglycol type lubricants are long chain linear polymers formed by the reaction of an aliphatic alcohol or a phenol with an epoxide material such as ethylene 3 I le, propylene oxide, butylene oxide, or the like. This s of lubricants contains repeating ether groups in the rmer chain which are generally terminated with a roxyl group. In some instances, the hydroxyl group locked by formation of an alkoxy end group or by rification of the terminal hydroxyl radical with an lnic acid.

he phosphate esters are a class of lubricant materials so chief beneficial characteristic is their lack of flamility. The most important of these lubricants are the esters of phosphoric acid, which have good lubricity, film strength and are non-corrosive. Examples of l phosphate esters include tricresylphosphate, trixylylaphate, and the like.

he silicone lubricants are polymeric materials coning the elements silicon and oxygen and organic lps. The backbone of the polymer contains. repeatsilicon-oxygen units which can be represented by the iula:

rein the R groups can be the same or different orradicals such as methyl, ethyl, propyl, amyl, benphenyl, and the like. The most important silicone lulnts are those in which the R groups are the methyl :al. The molecular weight of the silicone lubricants :ated by the average value of 2: depends on the deof polymerization and varies from about 162 to over 000. Some examples .of silicone lubricants include :th'yl polysiloxanes, diethyl polysiloxanes, diamyl siloxanes, meth'ylethyl polysiloxanes, methyl phenyl siloxanes, diphenyl polysiloxanes, and di-p-chloroyl polysiloxanes.

licate esters include both the ortho-silicate esters and timer silicate esters. The ortho-silicate esters are mals having the formula:

SitOR) 4 ein the R groups are the same or different organic als such as alkyl, aryl, or mixed alkyl-aryl. These be substituted by such groups as chloro, nitro, lluoro, (y, thioalkoxy, and the like. The ortho-silicatc esters :ometimes referred to as tetraalkoxy or tetraaryloxy es. However, the silanes contain carbon silicon bonds the properties of the two types of lubricants are diflt. Dimer silicate esters are similar to the ortho-siliand have the structure:

ein the R groups can be any organic radical which be the same or dilierent. Furthermore, as was the with the orthosilicate esters, these organic radicals be substituted with a variety of common substitu- The dimer silicate esters are frequently referred to exaalkoxy or hexaaryloxy disiloxanes. Some examof silicate ester lubricants include tetrapropoxy sildimethoxy dihexoxy silane, tributoxy phenoxy silhexamethoxy disiloxane, hexabutoxy disiloxane, trioxy tripropoxy disiloxane, tetra-Z-ethylhexoxy siltetra p tert butylphenoxy silane, tetra p chloro oxy silane, and hexa-p-chloro phenoxy disiloxane. lyphenyl ethers are compounds in which aromatic ps are connected through oxygen bridges. The arogroups can besimple phenylene radicals or substiphenylene radicals. For example, 2,6-dimethylphean be converted to a polyphenyl ether with repeating imethylphenylene groups lbonded through oxygen s. This is accomplished by treatment of 2,6-dimeth- :nol with oxygen in the presence of a cupric chlonnine catalyst. Preferably, the repeating arylene ps are bridged at different positions such as the ortho, meta and para positions because this results in a lower melting lubricant. Some examples of polyphenyl.

phenoxylbenzene, p di(p tert butylphenoxy) benzene,

di(p chlorophenoxylbenzene, and p di(p methoxyphenoxy)benzene.

Pluoroester lubricants are esters of fluoro acids and fluoro alcohols. The fluoro acids include both perfluoro monoand di-carboxylic acids. Typical acids include nonafluoropentanoic acid, SH-octafluoropentanoic acid, and the like. Typical fiuoro alcohols are 1H,1H-nonafluoro-lpentanol, 1H,1H,5H octafluoro 1 pentanol, and the like. These materials result in such esters as 1H,lH-nonafiuoropentyl nonafiuoropentanoate, lH,lH,5H octafluoropentyl-SH-octafluoropentanoate, and the like. Other fiuoro esters can be prepared by the esterification of a fiuoro alcohol with a non-fluoro organic acid or by the esterification of a non-fluoro alcohol with a fluoro acid employing catalysts such as p-toluene sulfonic acid.

A preferred embodiment of the present invention is a lubricant composition which contains a substantial amount, in excess of about 10 percent and preferably over 50 percent, of an ester type lubricant and a stabilizing amount of the synergistic combination of a phenothiazine is especially benefited by the synergistic eifect of the trihydrocarbyl tin sulfide. Ester lubricants include all the synthetic lubricants which are esters of an organic acid and an alcohol. These may be simple esters of monobasic organic acids and monohydroxyl alcohols, esters of polybasic organic acids and monohydroxyl alcohols, esters'of monobasic organic acids and polyhydroxyl alcohols, complex esters of polybasic organic acids bridged by polyhydroxyl alcohols or polyglycols having terminal ester groups derived from monohydroxyl alcohols and esters of polybasic acids and polyhydroxyl alcohols or polyglycols with monobasic organic acid ester groups in the terminal position. Various types of ester lubricants are set forth in Synthetic Lubricants, ibid, p. 151-245 and p. 388-401.

The following classification describes the preferred types of ester lubricants. In the first class are esters having the formula:

laurate, n-cetyl stearate, n-decyl palmitate, Z-ethylhexylpelargonate, 2,2,3-trimethylpentyl propionate, dilauryl succinate, di-Z-ethylhexyl glutarate, di-3,4-dimethylhexyl adipate, di-4-,5-dimethylpentyl pimelate, di-3-methylheptyl suberate, 2-ethy1hexyl-2,3-dimethylhexyl azelate, di-2,3-dimethyloctyl adipate, di-2,3,3-trimethyldodecyl succinate, di-Z-ethylhexyl sebacate, di-2-ethylhexyl amlate, di-Z-ethylhexyl adipate, tri-butyl aconitate, tri-Z- ethylhexyl aconitate, tri-Z-ethylhexyl tricarballylate, dibutyllauryl aconitate.

0f the foregoing class of esters, the more preferred are the esters of adipic, sebacic and azelaic acid and monohydroxyl alcohols containing from 6 to 12 carbon atoms. The most preferred esters are those of these acids formed from branched chain primary aliphatic alcohols containing from about 6 to 12 carbon atoms. The most highly preferred esters are dioctyl esters, especially di-Z-ethylhexyl sebacate, di-2-ethylhcxyl adipate and di-2-ethylhexyl azelate.

The next class of esters benefited by this invention are those having the formula:

wherein R is selected from the group consisting of hydrocarbon radicals having valence m and containing from about 2 to carbon atoms and polyalkyleneoxy radicals wherein each alkylene radical contains from 2 to 3 carbon atoms, R is an alkyl radical containing from about 4 to carbon atoms, and m is an integer from 2 to 4. These esters are exemplified by: ethylene glycol divalerate, propylene glycol dilaurate, hexamethylene glycol dihexoate, decamethylene glycol diarachidate, neopentyl glycol dicaproate, ethylene glycol dipelargonate, diethylene glycol dipelargonate, neopentyl glycol dipelargonate, tripropylene glycol dipelargonate, neopentyl glycol didecanoate, neopentyl glycol dilaurate, trimethylolpropane trivalerate, trimethylolpropane trihexanoate, trimethylolethane tri; heptanoate, trimethylolethane trilaurate, trimethylolbutane n'ivalerate, trimethylolbutane triheptanoate, trimethylolbutane trilaurate, trimethylolhexane trivalerate, trimethylolhexane divalerate heptanoate, trimethylolhexane dilaurate valerate, pentaerythritol tetravalerate, pentaerythritol tetralaurate, pcntaerythritol divalerate distearate, pentaerythritol tetrahexanoate, pentaerythritol tetraheptanoate.

Of the foregoing, the most preferred esters are those of trimehtylolpropane with fatty acids containing from 5 to about 12 carbon atoms such as trimethy'lolpropane trivalerate, trimethylolpropane tripelargonate, trimethylolpropane tridodecanoate and mixtures containing these ester groups.

Still another useful class of ester lubricants are glycolcentered complex esters having the formula:

wherein R and R are alkyl radicals containing from about 4 to 16 carbon atoms, R, and R are divalent hydrocarbon radicals containing from about 2 to 16 carbon atoms, R is an alkylene radical containing from 2 to about 10 carbon atoms, p has an average value of from about 1 to 6, and q has an average value of from about l to 3. These lubricants find use where a high viscosity lubricant is desired. These esters are formed by reacting about one mole of an alkylene glycol or polyalkylene glycol with about 2 moles of a dibasic organic acid so that the major product formed is the half-ester of the dibasic organic acid in which two molecules of the dibasic organic acid are joined at one end together through the glycol or polyglycol molecule. Of course, some of the molecules will contain two or more dibasic acid units since both the acid and the glycol are bi-functional. Likewise, some dibasic acid will remain unesterified. The result is a mixture of products such that the average value of q in the above Formula HI varies from 1 to about 3. The terminal groups on each of the molecules is an acid group. To finish the ester these terminal groups are esterified with a mono-functional alcohol containing from about 4 to 16 carbon atoms. Due to the complex nature of these esters they are best illustrated by means of the following table, in which each of the units in the ester represented by Formula 111 is set forth for different typical products.

R and R6 R1 nd Rs P (avg.)

Cetyl Z-ethylhoxyl -(CH )a- Another class of dibasic acid-centered complexesters related to the above consists of those having the formula:-

wherein R and R are alkyl radicals containing about 4 to 20 carbon atoms, R and R are alkylene radicals containing from 2 to about 10 carbon atoms, R is a divalent hydrocarbon radical containing from about 2 to 16 carbon atoms, r and s have an average value of from about 1 to 6, and t has an average value of from about 1 to 3.

These complex dibasic acid ester lubricants are prepared by reacting about one mole equivalent of a dibasic acid containing about 4 to 18 carbon atoms with 2 to 3 mole equivalents of a glycol or polyglycol wherein each repeating alkylene unit contains about 2 to 4 carbon atoms, forming a diester wherein each ester group is terminated bya hydroxyl radical. The ester formation is completed by reacting these terminal hydroxyl radicals with a monobasic fatty acid containing about 5 to 20 carbon atoms. As was the case with the glycol-centered complex ester of Formula III, the dibasic acid complex esters of Formula IV are best illustrated by the following table showing typical Formula IV units.

r and s R10 and Ru Ru a d rs R14 (avg) t (avg) n-Butyl -(CH2)2 -CH2)a 4. 5 1. 0 n-OctyL CHOH2 OHz)r 2 1. 5

H: I n-Octadecyl (CH2)4 -(CH2)7- 6 3 2-ethyluonyl. -(CH:) (CH2)m- 1 1. 2

The following examples illustrates the stabilizing com-. positions of this invention that are useful as additives to a variety of base lubricants. Percentages are on a weight basis.

(1 50%phenothiazine 50%tributyl tin sulfide (2) 99%-phenotriazine 1%--tri'butyl tin sulfide (3) l0%phenotriazine %--triethyl tin sulfide (4) 75 %--phenothiazine 25%tri-n-octyl tin sulfide (5) 90%3,7-dioctyl phenothiazine l0%-triphenyl tin sulfide (6) 80%3,7-di-tert-butyl phenothiazine 20% -tribenzyl tin sulfide (7) %-1,9-diethyl-3,7-dichloro phenothiazine 5%tri(2-ethylhexyl) tin sulfide (8) 99%1,3,7,9-tetra-methyl phenothiazine 1%-tri(2-ethyloctadecyl) tin sulfide The following examples serve to illustrate typical base lubricants containing the synergistic stabilizers.

EXAMPLE 2 To 1000 parts of a polybutene synthetic lubricant made by the aluminum chloride catalyzed polymerization of isobutylene and having a viscosity equivalent to a SAE-30 oil is added one weight percent of 3-(1-methylpentadecyl) plenothiazine and 0.01 weight percent of triamyl tin sulfi e.

7 EXAMPLE 3 o 1000 parts of a butyl-terminated polypropylene glyhaving an average molecular weight of about 750 is :d 3 weight percent of 3,7-dioctyl phenothiazine and weight percent of tri(2-ethyloctyl) tin sulfide.

EXAMPLE 4 o 1000 parts of tricresylphosphate are added 5 weight ent of 3,7-difluoro'phenothiazine and 0.5 weight perof tribenzyl tin sulfide.

EXAMPLE 5 a 1000 parts of an ethoxy end-blocked dimethyl poly:

am having an average molecular weight of 3800 and scosity at 77 F. of .48 cs. is added 1 weight percent henothiazine and 0.07 weight percent of tri(p-nonyliyl) tin sulfide.

EXAMPLE 6 a 1000 parts of tetra-p-chlorophenoxy silane is added weight percent of 3,7-tri(2-ethylhexyl)phenothiazine 0.5..weight percent of diethyl tin sulfide.

I EXAMPLE 7 .1000 parts of m-phenoxyphenyl p-phenoxyphenyl is added 0.2 weight percent of 3,7-di (Z-methyloctyl) othiazine and 0.001 weight percent of dibutyl methyl ilfide.

EXAMPLE 8 r 1000 parts of 1H,1H,5H-octafluoropentyl 5H-octaopentanoate is added 0.01 weight percent of phenothiand 0.0005 weight percent of tributyl tin sulfide.

EXAMPLE 9 v 1000 parts of n-butyl pelargonate is added 0.5 weight :nt of phenothiazine and 0.005 weight percent of tril tin sulfide.

' EXAMPLE 10 I 1000 parts of l-methylnonadecyl butyrate is added :ight percent of 3,7-dioctyl phenothiazine and 0.05

at percent of trimethyl tin sulfide. 1

EXAMPLE 11 1000 parts of di(2-ethylhexyl)adipate is added 0.5 it percent of phenothiazine and 0.05 weight percent 'lethyl tin sulfide.

EXAMPLE 12 I 1000 parts of di(2-ethylhexyl)sebacate is added 1 1t percent of phenothiazine and 0.005 weight percent butyl tin sulfide.

EXAMPLE 15 l 1000 parts of hexamethyleneglycol dihexoate is d 0.8 weight percent of 3,7 -dichlorophenothiazine an 5 weight percent of triamyl tin sulfide.

EXAMPLE 16 r 1000 parts of ethyleneglycol pelargonate is added veight percent of phenothiazine and 0.01 weight perof tributyl tin sulfide.

8 EXAMPLE 17 To 1000 parts of trimethylolpropane trivalerate is added 1 weight percent of phenothiazine and 0.007 weight percent of tributyl tin sulfide.

EXAMPLE 18 To.1000 parts of pentaerythritol tetrapelargonate is added 0.5 weight percent of phenothiazine and 0.05 weight percent of tributyl tin sulfide.

EXAMPLE 19 To 1000 parts of a glycol-centered complex ester formed by the acid catalyzed esterification reaction of one mole equivalent of hexamethylene'glycol with two mole equivalents of sebacic acid followed by esterification with two mole equivalents of 2-ethylhexano1 is added 1 weight per cent of 3,7-di(1-methylnonyl)phenothiazine and 0.01 weight percent of triamyl tin sulfide.

EXAMPLE 20 To 1000. parts of a poIyglycol-centered complex ester formed by the acid catalyzed esterification reaction of B H R wherein each R is selected from the group consisting of hydrogen, alkyl groups containing 1 to 20 carbon atoms, aryl groups containing 6 to 20 carbon atoms and aralkyl radicals containing 7 to 20 carbon atoms, and from 1 to about weight percent of a trihydrocarbyl tin sulfide wherein the hydrocarbyl radicals contain from 1 to about 20 carbon atoms.

2. The stabilizer of claim 1 comprising from about 75 to 99 weight percent of phenothiazine and from about 1 to 25 weight percent of a trialkyl tin sulfide wherein the alkyl radicals contain from 1 to about 12 carbon atoms.

'3. The stabilizer composition of claim 2 wherein said trialkyl tin sulfide is trimethyl tin sulfide.

4. The stabilizer composition of claim 2 wherein said trialkyl tin sulfide is tributyl tin sulfide. I

5. A stable lubricant composition comprising, as a major component, a synthetic ester base lubricant and, as a minor component, a stabilizing amount of a composition of claim 1.

6. The lubricant composition of claim 5 wherein said synthetic ester lubricant is selected from the group of compounds having the formulae:

wherein R is a. hydrocarbon radical having valence n and containing from about 2 to about 17 carbon atoms, R, is an alkyl radical containing from about 4 to 16 carbon atoms, and n is an integer from 1 to 3;

Rr-EO-E-Bq wherein R is selected from the group consisting of hydrocarbon radicals having valence m and containing from about 2 to 10 carbon atoms and polvalkyleneoxy radicals wherein each alkylene radical contains from 2 to 3 carbon atoms, R; is an alkyl radical containingfrom about 4 to 20 carbon atoms, and m is an integer from 2 to 4;

wherein R and R are alkyl radicals containing about 4 to 20 carbon atoms, R and R are alkylene radicals containing from 2 to about 10 carbon atoms, R is a divalent hydrocarbon radical containing from about 2 to 16 carbon atoms, r and s have an average value of from 10 about 1 to 6, and t has an average value of from about 1 to 3.

7. The lubricating oil composition of claim 6 wherein said ester lubricant is a C dialkyl sebacate.

8. The lubricating oil composition of claim 7 wherein said ester lubricant is a dioctyl sebacate.

9. The lubricating oil composition of claim 7 wherein said ester is di(2-ethylhexyl)sebacate.

10. The lubricant composition of claim 9 containing from about 0.01 to 5 weight percent of phenothiazine and from about 0.0005 to 0.5 weight percent oftributyl tin sulfide.

11. The lubricant composition of claim 6 wherein said ester lubricant is trimethylolpropane tripelargonate.

References Cited UNITED STATES PATENTS 6/1942 Lincoln 252 -46.4 x 4/1957 Weinberg et a1. 260"429.7 X

FOREIGN PATENTS 907,664 10/ 1962 Great Britain.

" UNITED STATES PATENT OFFICE 5 CERTIFICATE OF CORRECTION Patent No. 5 5 ,7 Dated May 12, 1970 Inventor(fi) Roberfix E. lflalec It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

rzblumh 5, lines 59-40, that portion of the formula reading: -1

O O O n u should u 8 R OCR -CC read R OCR -CO-- Column 6, line M2, phenotrlazihe should read phenothiazine line MU, phenotriazihe should read phenothiazine Column 8, Claim 6(B), in the formula, omit the bond after "R SIGNED AND SEALED SEPISM @HHHQ Amumu Edward M. Fletcher, Jr. mm

a E. JR- Attestmg Officer Commissioner of Patents 

